Multi-mode antenna system for a computing device and method of operation

ABSTRACT

An antenna system for a computing device operable in multiple communication modes.

FIELD OF THE INVENTION

[0001] The invention relates generally to wireless computer networkingand, more particularly, to a multi-mode antenna system for a computingdevice.

BACKGROUND OF THE INVENTION

[0002] Portable computing devices—such as laptop computers, notebookcomputers, tablet style computers, hand-held computing devices (e.g., apersonal digital assistant, or PDA), and the like—have become nearlyubiquitous as their desktop relatives. Users of portable computers oftenneed access to a computer network yet, due to their mobility, a user ofsuch a portable device may not have access to a wired networkconnection. Thus, the ability to access a network via a wireless networkconnection, or otherwise to conduct wireless communications, is highlydesirable for these mobile computing devices.

[0003] Mobile computer users may need to conduct wireless networkingactivities in a variety of network environments at different times oreven simultaneously. By way of example, a user may wish to communicatewirelessly over a relatively short range with a network or withindividual devices (e.g., printers and other peripherals). A network—or,more generally, a wireless connection between two or more devices—thattakes place over a relatively short range (e.g., up to 10 meters) issometimes referred to as a Personal Area Network, or PAN. The user mayalso need to establish a wireless connection with a Local Area Network,or LAN. A typical wireless LAN connection may extend over a range of,for example, from 10 to 100 meters. Further, the user of this mobilecomputing device may want to establish a wireless connection with anetwork over a relatively long range (e.g., greater than 100 meters). Anetwork extending over a vast region is often referred to as a Wide AreaNetwork, or WAN.

[0004] One technology used for establishing wireless PAN connections isBluetooth™. Bluetooth is a short range, low power radio technology thatsupports both voice and data applications, and this technology providesfrequency-hopping spread spectrum (FHSS) radio connections over multiplechannels in the 2.4 GHz radio band (more precisely, in the 2.4 to 2.4835GHz band). Bluetooth wireless technology generally supports a range upto 10 meters, although longer distances are possible with more powerfulradios.

[0005] A wireless LAN technology is defined in the IEEE (Institute ofElectrical and Electronics Engineers) 802.11 family of specifications,including 802.11a and 802.11b. The IEEE 802.11b standard defineswireless services over a 2.4 GHz band that spans a frequency range of2.4 to 2.4835 GHz, whereas IEEE 802.11a defines wireless services over anumber of bands in the 5 GHz frequency range, including 5.15 to 5.25GHz, 5.25 to 5.35 GHz, and 5.725 to 5.825 GHz.

[0006] A technology useful for wireless WAN communications is theGeneral Packet Radio Service, or GPRS. GPRS provides wireless,packet-based services over a GSM™ (Global System for MobileCommunications) network. A GSM network can be implemented in anyfrequency band; however, there are several frequency bands that arecurrently (or will shortly be) in use, including GSM400 (450.4-457.6 MHzand 460.4-467.6 MHz or 478.8-486 MHz and 488.8-496 MHz), GSM850 (824-849MHz and 869-894 MHz), GSM900 (880-915 MHz and 925-960 MHz), GSM1800(1710-1785 MHz and 1805-1880 MHz), and GSM1900 (1850-1910 MHz and1930-1990 MHz).

[0007] Despite the availability of the above-described technologies, aswell as others, to conduct wireless network communications at variousfrequencies, in a number of environments (e.g., a PAN, LAN, or WAN), andover various distances, a typical portable computing device is equippedor configured to operate in only one wireless RF (radio frequency)communications mode. A number of parameters may characterize aparticular RF communications mode, including frequency, range ordistance, networking environment (e.g., PAN, LAN, or WAN), and thecommunications standard or technology (e.g., Bluetooth, IEEE 802.11a and802.11b, GPRS, etc.). A wireless RF communication mode will be referredto herein as simply a “mode.”

[0008] A single mode computing device generally has one antennaoptimized for that communication mode. For example, a portable computermay have a single antenna that is designed for wireless Bluetoothservices in the 2.4 GHz band and, further, that is optimized for useover a relatively short range. However, this antenna may function poorlyin other modes (e.g., in IEEE 802.11a or in a GPRS mode).

[0009] A variety of peripheral cards (e.g., PC Cards, PCI cards, etc.)providing wireless networking capabilities are presently available, andit may be possible to adapt a portable computer for use in multiplemodes (e.g., for both Bluetooth in the 2.4 GHz band and IEEE 802.11a inthe 5 GHz band). However, adapting a portable computing device forwireless networking in multiple modes using add-on peripheral cards maybe impeded by space constraints, as space is generally at a premium inportable computers. Further, the placement of multiple antennas—each foruse with a different mode—on a portable computing device presentsco-existence problems, as a lack of isolation between antennas may leadto interference and cross-talk.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic diagram illustrating an embodiment of acomputing device having an antenna system providing multiple modes.

[0011]FIG. 2A is a schematic diagram illustrating one embodiment of themulti-mode antenna system shown in FIG. 1.

[0012]FIG. 2B is a schematic diagram illustrating another embodiment ofthe multi-mode antenna system shown in FIG. 1.

[0013]FIG. 3 is a schematic diagram illustrating an embodiment of thecomputing shown in FIG. 1.

[0014]FIG. 4 is a perspective view of another embodiment of thecomputing device shown in FIG. 1.

[0015]FIGS. 5A and 5B are schematic diagrams illustrating an embodimentof a coventional antenna having an artificial magnetic conductor (AMC).

[0016]FIG. 6A is a side elevation view illustrating one embodiment ofthe computing device shown in FIG. 4.

[0017]FIG. 6B shows a cross-sectional view of the computing device ofFIG. 4, as taken along line a-a of FIG. 6A.

[0018]FIG. 7 is a perspective view of a further embodiment of thecomputing device shown in FIG. 1.

[0019]FIG. 8 is a plot of gain vs. azimuth angle for an antenna in freespace.

[0020]FIG. 9 is a plot of gain vs. azimuth angle of the antenna, asmounted on a computing device.

[0021]FIG. 10 is a plot of gain vs. percentage of azimuth angles with agiven value of gain for the antenna, as mounted on the computing device.

[0022]FIG. 11 is a flow chart illustrating an embodiment of a method ofselecting an antenna having desired characteristics.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Embodiments of an antenna system providing wirelesscommunications in a number of modes are described below. The disclosedembodiments of the multi-mode antenna system may find use in a widearray of computing devices, including laptop computers, notebookcomputers, tablet style computers, hand-held computing devices such asPDAs, as well as other mobile computing devices. However, it should beunderstood that, although described below in the context of portablecomputing devices, the disclosed embodiments are not so limited inapplication and, further, that the disclosed embodiments may find use indesktop computers and other less mobile computing devices. In additionto the embodiments of a multi-mode antenna system described below, alsodisclosed are the use of AMC-based antennas, embodiments of antennamounting and isolation, interference and embodiments for providingisolation between antennas, and embodiments of a method for antennaselection and evaluation.

A. Multi-Mode Antenna System

[0024] Referring to FIG. 1, a computing device 100 includes a multi-modeantenna system 200. The computing device 100 may comprise any one of theabove described computing devices, including a portable computer or adesktop computer. The multi-mode antenna system 200 provides computingdevice 100 with the capability to establish network connections inmultiple modes, wherein a particular mode may be characterized by anumber of parameters, including frequency, specification (e.g.,Bluetooth, IEEE 802.11a and 802.11b, GPRS, etc.), networking environment(e.g., PAN, LAN, WAN, as well as others, such as a metropolitan areanetwork, or MAN, and a system area network, or SAN), and range. Themulti-mode antenna system 200 may comprise any suitable number andcombination of antenna elements, and each of the antenna elements maycomprise any suitable type of antenna. Generally, each of the antennaelements of antenna system 200 will provide for one mode ofcommunication; however, in other embodiments, a single antenna mayprovide for two or more modes.

[0025] Antenna system 200 is capable of conducting networkcommunications in multiple modes with a number of nodes. As used herein,the term “node” refers to any addressable device (or combination ofdevices), including routers, switches, computers, servers, andperipherals such as printers, as well as cellular base stations andsatellite terminals. For example, in the embodiment of FIG. 1, antennasystem 200 operates in a first mode 291 with a node 5 a, in a secondmode 292 with a node 5 b, and in a third mode 293 with a node 5 c.

[0026] Each of the modes 291, 292, 293 may have any desiredcharacteristics. In one embodiment, a mode is characterized by aspecified operating frequency. In another embodiment, a mode iscompatible with a certain specification or technology. In a furtherembodiment, a mode is conducted within a particular networkingenvironment. In yet another embodiment, a mode is characterized by adesired range. It should be understood that a mode may having any one ormore of these characteristics (or others).

[0027] First mode 291 is, in one embodiment, characterized by anoperating frequency in the 2.4 GHz band and, in a further embodiment,the first mode 291 is compatible with the Bluetooth™ specification. See,e.g., Specification of the Bluetooth System: Core, Vol. 1, Ver. 1.1,February 2001, promulgated by the Bluetooth Special Interest Group (SIG)and available at http://www.bluetooth.com. In a further embodiment, thefirst mode 291 comprises a wireless PAN connection and, in yet anotherembodiment, this PAN connection has a range up to approximately 10meters, or other suitable range.

[0028] Second mode 292 is, in one embodiment, compatible with the IEEE802.11 family of specifications. For example, the wireless connectionwith node 5 b may be based upon the 802.11a specification or,alternatively, based upon the 802.11b specification. See, e.g., IEEE Std802.11a-1999, Supplement to IEEE Standard for InformationTechnology—Telecommunications and Information Exchange BetweenSystems—Local and Metropolitan Area Networks—SpecificRequirements—Part11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications—High-Speed Physical Layer in the 5GHz Band (herein “IEEE 802.11a”), and IEEE Std 802.11b-1999, Supplementto IEEE Standard for Information Technology—Telecommunications andInformation Exchange Between Systems—Local and Metropolitan AreaNetworks—Specific Requirements—Part 11: Wireless LAN Medium AccessControl (MAC) and Physical Layer (PHY) Specifications—Higher-SpeedPhysical Layer Extension in the 2.4 GHz Band (herein “IEEE 802.11b”).For IEEE 802.11a, the second mode 292 is characterized by an operatingfrequency in the 5 GHz band, and for IEEE 802.11b, the second mode 292is characterized by an operating frequency in the 2.4 GHz band. In afurther embodiment, the second mode 292 comprises a wireless LANconnection and, in yet another embodiment, this LAN connection canoperate at ranges up to approximately 100 meters, or other suitablerange.

[0029] Third mode 293 is, in one embodiment, characterized by anoperating frequency selected from a frequency between 450 MHz and 1990MHZ and, in another embodiment, the third mode 293 is compatible withthe GPRS. See, e.g., Permanent Reference Document (PRD) IR.33, GPRSRoaming Guidelines, Ver. 3.1.0, April 2000, and PRD IR.40, Guidelinesfor Ipv4 Addressing and AS Numbering for GPRS Network Infrastructure andMobile Terminals, Ver. 3.1.0, September 2001, both available from theGSM™ Association at http://www.gsmworld.com. In a further embodiment,the third mode 293 comprises a wireless WAN connection and, in yetanother embodiment, this WAN connection can operate at ranges up toseveral kilometers (or other suitable range). Note that for relativelylarge distances (e.g., greater than 1000 meters), such a WAN connectionmay take place over both cellular telecommunication and/or satellitemediums and, due to the locations of cell sites, provide nearlycontinuous coverage.

[0030] For the embodiment shown in FIG. 1, it should be understood that,although only one node 5 a is shown communicating with computing device100 over the first mode 291, only one node 5 b is shown communicatingwith computing device 100 over the second mode 292, and only one node 5c is shown communicating with computing device 100 over the third mode293, computing device 100 may communicate with any suitable number ofnodes within each of the modes 291, 292, 293. Also, computing device 100may simultaneously communicate with multiple nodes across differentmodes. For example, the computing device 100 may have a Bluetoothcompatible connection with one or more nodes while simultaneouslycommunicating with one or more nodes over a GPRS compatible connection.In a further example, in addition to the simultaneous connections withnodes using Bluetooth and GPRS, the computing device may alsosimultaneously maintain a connection with one or more nodes using eitheran IEEE 802.11a or 802.11b compatible connection.

[0031] Embodiments of the multi-mode antenna system 200 are illustratedin FIGS. 2A and 2B, respectively. Referring to FIG. 2A, the antennasystem 200 includes three antennas 210, 220, 230. The first antenna 210is capable of communications over the first mode 291 (e.g., with node 5a), the second antenna 220 is capable of communications over the secondmode 292 (e.g., with node 5 b), and the third antenna 230 is capable ofcommunications over the third mode 293 (e.g., with node 5 c).

[0032] In one embodiment, first antenna 210 has an operating frequencyin the 2.4 GHz band (i.e., between 2.4 and 2.48 GHz). In anotherembodiment, the first antenna 210 is compatible with the Bluetoothspecification. In a further embodiment, the antenna 210 is capable ofestablishing PAN connections and, in yet another embodiment, the firstantenna 210 has a range of approximately 10 meters, or other suitablerange.

[0033] In one embodiment, second antenna 220 has an operating frequencyin the 2.4 GHz band (i.e., between 2.4 and 2.48 GHz) and, in anotherembodiment, has an operating frequency in the 5 GHz band (i.e., between5.15 and 5.825 GHz). In a further embodiment, the second antenna 220 iscompatible with the IEEE 802.11 family of specifications (e.g., eitherIEEE 802.11a or 802.11b). In yet another embodiment, second antenna 220is capable of establishing LAN connections and, in yet a furtherembodiment, the second antenna 220 has a range up to approximately 100meters, or other suitable range.

[0034] In one embodiment, third antenna 230 has an operating frequencybetween 450 MHz and 1990 MHz and, in another embodiment, the thirdantenna 230 is compatible with the GPRS. In a further embodiment, thirdantenna 230 is capable of establishing WAN connections and, in yet aanother embodiment, the third antenna 230 has a range up to severalkilometers and greater (or other suitable range).

[0035] The embodiment of antenna system 200 illustrated in FIG. 2B issimilar to that shown in FIG. 2A; however, the antenna system 200 ofFIG. 2B includes a fourth mode of operation 294. Turning now to FIG. 2B,the antenna system 200 includes the three antennas 210, 220, 230, asdescribed above, as well as a fourth antenna 240. The fourth antenna iscapable of communications over the fourth mode 294 (e.g., with node 5d). In one embodiment, each of the second and fourth modes 292, 294 iscompatible with one of IEEE 802.11a and 802.11b. Thus, one of the secondand fourth antennas 220, 240 is compatible with IEEE 802.11a and theother of these antennas is compatible with IEEE 802.11b. In anotherembodiment, both of the second and fourth antennas 220, 240 are capableof establishing LAN connections and, in yet a further embodiment, eachof the second and fourth antennas has a range up to approximately 100meters, or other suitable range.

[0036] In a further embodiment of antenna system 200, two or more of theantennas may comprise a single integrated antenna. For example, for theembodiment of FIG. 2A, the first antenna 210 (e.g., providing a firstmode 291 that is Bluetooth compatible and characterized by an operatingfrequency in the 2.4 GHz band) may be integrated with the second antenna220 (e.g., providing a second mode 292 that is IEEE 802.11a compatibleand characterized by an operating frequency in the 5 GHz band) as asingle antenna. By way of further example, for the embodiment of FIG.2B, the second antenna 220 (e.g., providing a second mode 292 compatiblewith IEEE 802.11b and characterized by an operating frequency in the 2.4GHz band) may be integrated with the fourth antenna 240 (e.g., providinga fourth mode compatible with IEEE 802.11a and characterized by anoperating frequency in the 5 GHz band) as a single antenna.

[0037] It should be understood that the embodiments of antenna system200 shown and described with respect to FIGS. 2A and 2B are but a fewexamples of multi-mode antenna systems. Those of ordinary skill in theart will appreciate that such a multi-mode antenna system may includeany suitable number, type, and combination of antennas. Further, as willalso be appreciated by those of ordinary skill in the art, a mode may becharacterized by characteristics other than those described above.

[0038] Referring to FIG. 3, an embodiment of computing device 100 isillustrated. Computing device 100 includes a bus 105 having a processingdevice (or devices) 110 coupled therewith. The processing device 110 maycomprise a microprocessor, an application specific integrated circuit(ASIC), or a field programmable gate array (FPGA), as well as any othersuitable processing device. Computing device 100 also includes systemmemory 120 coupled with bus 105, the system memory 120 comprising, forexample, any suitable type of random access memory (RAM). Duringoperation, the system memory 120 may have an operating system residentthereon. The computing device 100 may further include a read-only memory(ROM) 130 coupled with the bus 105. During operation, the ROM 130 maystore temporary instructions and variables for processing device 110,and ROM 30 may also have resident thereon a system BIOS (BasicInput/Output System).

[0039] Computing device 100 may include a storage device 140 coupledwith the bus 105. The storage device 140 comprises any suitablenon-volatile memory, such as, for example, a hard disk drive. Also, adevice 150 for accessing removable storage media—e.g., a floppy diskdrive or a CD ROM drive—may be coupled with bus 105. Further, computingdevice 100 may include one or more input devices 160 and one or moreoutput devices 170 coupled with the bus 105. Common input devices 160include keyboards, pointing devices such as a mouse, and scanners orother data entry devices, whereas common output devices 170 includevideo monitors and displays, printing devices, and audio output devices(e.g., a sound card and speakers). Note that peripheral devices (e.g.,printers, etc.) may be coupled with the computing device 100 via awireless network connection (e.g., a Bluetooth compatible connection)established using antenna system 200.

[0040] Computing device 100 further comprises a network interface 180coupled with bus 105. The network interface 180 comprises any suitablehardware, software, or combination of hardware and software capable ofmaintaining a network connection with one or more nodes over any one (ormore) of the first, second, and third modes 291, 292, 293 (and/or fourthmode 294). Network interface 180 is coupled with the multi-mode antennasystem 200, as shown in FIG. 3.

[0041] It should be understood that the computing device 100 illustratedin FIG. 3 is intended to represent an exemplary embodiment of such acomputer system and, further, that this computer system may include manyadditional components, which have been omitted for clarity and ease ofunderstanding. By way of example, the computing device 100 may include aDMA (direct memory access) controller, a chip set associated with theprocessing device 110, additional memory (e.g., a cache memory), as wellas additional signal lines and buses. Also, it should be understood thatthe computing device 100 may not include all of the components shown inFIG. 3.

[0042] Illustrated in FIG. 4 is a further embodiment of the computingdevice 100. In the embodiment of FIG. 4, the computing device 100includes a housing 190 comprised of a first housing 190 a and a secondhousing 190 b. The housing elements 190 a, 190 b are movably coupledtogether by a connector 195. For example, as shown in FIG. 4, theconnector 195 may comprise a hinge allowing relative rotation betweenthe first housing 190 a and the second housing 190 b. The housing 190may be constructed of any suitable material (or materials), includingmetals, plastics, and composite materials.

[0043] Disposed in the second housing 190 b are a keyboard 160 a and atrack pad (or track ball or mouse) 160 b. A display 170 (e.g., a liquidcrystal display, or LCD) is disposed in the first housing 190 a.Although not shown in FIG. 4, the computing device 100 may include aprocessing device, system memory, ROM memory, hard disk drive, a networkinterface, a floppy disk drive, as well as other input and outputdevices, such devices typically being disposed within the second housing190 b.

[0044] Antenna system 200 is disposed in the first housing 190 a. In theembodiment of FIG. 4, the antenna system 200 is essentially the same asthat shown and described above in FIG. 2B and includes four antennas210, 220, 230, 240 (disposed on edge surfaces 197, 198, 199 of firsthousing 190 a). The first, second, third, and fourth antennas 210, 220,230, 240 are capable of performing communications over the first,second, third, and fourth modes 291, 292, 293, 294, respectively.Various embodiments of each of the first, second, third, and fourthmodes 291, 292, 293, 294 are described above. In other embodiments,however, the computing device 100 may include more or fewer (e.g., seeFIG. 2A) antennas and/or modes.

[0045] It is to be understood that the embodiment of computing device100 shown in FIG. 4 is but one example of the configuration of acomputing device. As previously noted, the computing device 100 maycomprise any laptop computer, notebook computer, tablet style computer,hand-held computer, or other portable computing device, as well as adesktop computer or other less mobile computer platform. If thecomputing device 100 is a tablet style computer, the connector 195 mayallow the first housing element 190 a to be detached from the secondhousing element 190 b, such that the user may carry only the firsthousing element 190 a. With the keyboard and track pad 160 a-b detachedfrom the first housing element 190 a, data entry may take place at thedisplay 170 (e.g., through use of touch-screen technology). Also, for atablet style computer, components such as the processing device, ROM,and system memory may be disposed within the first housing element 190 aalong with the display 170.

B. AMC-Based Antennas

[0046] Each of the antennas 210, 220, 230, 240 may comprise any suitabletype of antenna. One type of antenna that may-be employed in themulti-mode antenna system 200 is illustrated in FIGS. 5A and 5B, whereinFIG. 5A shows a side elevation view of the antenna and FIG. 5B shows atop view of the antenna. Referring to FIGS. 5A-5B, the antenna 500includes a base 510 having an antenna element 520 disposed or formedthereon. The base 510 comprises an artificial magnetic conductor (AMC).

[0047] An AMC is an engineered electromagnetic material—typically formedusing printed circuit board technology—that reflects plane wavesin-phase at their resonant frequency. When an antenna element is placedin close proximity to an AMC material, the antenna element can radiateefficiently as though it were in free space. Also, use of AMC materialsin an antenna system can limit mutual coupling between adjacent antennaswith minimal power absorption and efficiency degradation. Thus, whenAMC-based antennas are utilized in antenna system 200, the antennasystem may exhibit improved isolation characteristics between antennas.Also, antennas disposed or formed on AMC substrates can be manufacturedin relatively small sizes with thin profiles. For example, an AMC-basedantenna 500 may have a height 502 of approximately 4 millimeters orless. Further, AMC-based antennas are generally less sensitive tocontact with hands and fingers than other types of antennas, which maylead to less detuning when the computing device 100 is being held ortouched by the user. Antennas utilizing these AMC materials areavailable from the Etenna Corporation of Laurel, Md.

C. Antenna Mounting and Isolation

[0048] Each of the antennas 210, 220, 230, 240 may be mounted on (orwithin) the first housing 190 a (or second housing 190 b) using anysuitable method or technology. For example, an antenna may be directlyattached to a surface of the first housing 190 a, an antenna may bemounted within a cavity formed on the exterior of the first housing 190a to provide a flush mount, or an antenna may be mounted within thefirst housing 190 a. An example of a surface mounted antenna is shown inFIG. 6A, and an example of a flush mounted antenna is illustrated inFIGS. 6A and 6B. The antennas may be secured to the housing 190 a usingadhesives, mechanical fasteners, or by any other suitable technique.Note that the above-described AMC materials can help to shield anantenna from noise generated by any processing device within housing190. Also, where a metal housing 190 is used to provide shielding fromany processing device located inside the housing, the use of AMCmaterials for surface-mounted antennas can help to isolate the antennafrom the metal housing itself.

[0049] Turning now to FIG. 6A, the antenna 230 is mounted on an uppersurface 197 of the first housing 190 a. The antenna 230 includes anantenna element 234 formed or disposed on a base 232 (e.g., an AMCsubstrate). The base 232 may be directly attached to the surface 197using adhesives, or the base 232 may be attached to the surface 197using mechanical fasteners (e.g., screws, brackets, pins, T-slots,dovetail slots, etc.). For certain types of antennas—e.g., AMC-basedantennas—the antenna 230 may extend a height 239 above the housingsurface 197 of approximately 4 millimeters or less.

[0050] Referring to both FIGS. 6A and 6B, the antenna 240 is mounted ina cavity 605 formed on an exterior surface 198 of the first housing 190a. The antenna 240—which, in the embodiment of FIGS. 6A-6B, has anL-shape configuration—includes an antenna element 244 formed or disposedon a base 242. In one embodiment, the base 242 comprises an RF absorbingmaterial to provide an improved impedance match. Base 242 may be securedwithin the cavity 605 using adhesives, or the base 242 may be securedwithin the cavity 605 using mechanical fasteners (e.g., screws,brackets, pins, T-slots, dovetail slots, etc.). Note that the cavity 605has a depth that is at least slightly greater than a height of theantenna 240, such that the antenna 240 is mounted flush and does notextend above the exterior housing surface 198.

D. Interference and Isolation Between Antennas

[0051] The close proximity of multiple antennas on a relatively smallcomputing device can create interference problems. Interference betweenantennas may be especially predominant when the frequency bands ofadjacent antennas overlap, such as when placing Bluetooth and IEEE802.11b compatible antennas near to one another (as noted above, bothBluetooth and IEEE 802.11b occupy a 2.4 GHz band). Isolation betweenantennas can be improved using AMC materials, as described above, anduse of these AMC materials for antenna isolation is illustrated in theembodiment of FIG. 7.

[0052] Referring now to FIG. 7, the computing device 100 includesisolation elements 701, 702. Isolation element 701 is disposed on firsthousing 190 a between antenna 210 (e.g., for a Bluetooth communicationsmode) and antenna 220 (e.g., for a IEEE 802.11b communications mode),and isolation element 702 is disposed on first housing 190 a betweenantenna 220 and antenna 230 (e.g., for a IEEE 802.11a communicationsmode). Of course, such isolation elements may be positioned in othersuitable locations. Generally, an isolation element 701, 702 comprisesany device (e.g., a coating or a separately attached part) and/ortechnique that provides isolation between antennas.

[0053] In one embodiment, each of the isolation elements 701, 702comprises a layer of AMC material disposed or formed on a surface of thehousing 190 a. The AMC material of each isolation element 701, 702 canbe tuned to attenuate signals in the appropriate band (e.g., the 2.4 GHzband). Use of AMC materials for isolation elements 701, 702 hasdemonstrated an improvement in attenuation from 25 dB (no isolationelements) to 45 dB. It should be understood, however, that othermaterials (and/or methods) may be employed for isolation between theantennas 210, 220, 230, 240, where necessary.

E. Antenna Selection and Evaluation

[0054] An embodiment of a method of selecting an antenna for the antennasystem 200 is now described with respect to FIGS. 8 through 11. Inparticular, the method can ensure a desired coverage margin for a givenantenna. It should be understood that the method described below withrespect to FIGS. 8 through 11 is but one example of a method by whichthe antenna system 200 may be designed and, further, that any suitableguidelines and design principles may be employed to design a multi-modeantenna system 200.

[0055] Initially, the desired range and frequency are specified (e.g.,up to 100 meters at a frequency in the 2.4 GHz band), and a desiredcoverage margin for the specified range is chosen (e.g., −4 dBi gain at80% of azimuth angles). The wireless RF system parameters also need tobe determined, including the transmitter power of the computing device100, the receive sensitivity of the destination node, and the antennagain of the destination node. Based upon this information, the gain ofthe source antenna (i.e., one of the antennas of computing device 100)can be calculated. In one embodiment, the source antenna gain isdetermined by the following equation (derived from the well known Friistransmission formula):

G _(t) =Rx _(sens) −P _(t) −G _(r)−(20)log₁₀(λ/4π)+(10)(n)log₁₀(d)  (1)

[0056] where G_(t)=gain of source antenna (dBi),

[0057] Rx_(sens)=receive sensitivity of destination node (dBm),

[0058] P_(t)=transmission power of source antenna (dBi),

[0059] G_(r)=gain of the destination node (dBi),

[0060] λ=wavelength (meters),

[0061] n=a path loss exponent determined from measurements (typically2.5 for an office environment), and

[0062] d=range (meters).

[0063] Once the required gain of the source antenna (G_(t)) has beenestimated from equation (1) above, an antenna can be selected andfurther evaluated. Evaluation of the selected antenna may includemeasuring the gain exhibited by the antenna as a function of azimuthangle to verify that the antenna provides the specified coverage margin.Illustrated in FIG. 8 is a plot 800 of gain vs. azimuth angle for theselected antenna in a stand-alone configuration (or in free space). Thegain curve 850 shows that the gain is relatively uniform for allazimuths; however, uniform gain across all azimuths is, in practice, notobtained. When the antenna is mounted on the computing device 100, thegain pattern exhibited by the antenna will be distorted. This isillustrated in FIG. 9, which shows a plot 900 of gain vs. azimuth anglefor the antenna, as mounted on computing device 100. Note that the gaincurve 950 varies significantly across all azimuths between a maximumgain 952 and a minimum gain 954. Referring to FIG. 10, shown is a plot1000 of gain vs. percentage of azimuth angles with a given value of gain(based upon the measured performance, as shown in FIG. 9). At 80% ofazimuth angles, the curve 1050 of gain vs. percentage azimuth angles hasa gain of approximately −4 dBi. Thus, the selected antenna has met thespecified coverage margin (i.e., −4 dBi at 80% of azimuth angles).

[0064] The above-described design methodology may be better understoodwith reference to FIG. 11, which illustrates a method 1100 of selectingan antenna having desired characteristics. Referring to block 1110 inFIG. 11, a range and frequency are selected (e.g., up to 10 meters in a2.4 GHz band). A coverage margin (e.g., −4 dBi at 80% of azimuths) isalso selected, as shown at block 1120. An antenna expected to meet thedesired coverage margin is then selected, which is illustrated at block1130. In one embodiment, the antenna is selected based upon an estimatedgain calculated using equation (1) above.

[0065] As shown at block 1140, the antenna's gain pattern is measuredacross all azimuths (or a selected number of azimuths) to determine thecoverage margin of the antenna. Referring to block 1150, if the coveragemargin has not been met, one or more parameters can be altered—see block1160—and the gain measurements repeated. Parameters that may be alteredinclude transmitter power of the source computing device (e.g.,computing device 100), the receive sensitivity of the destination node,and the antenna gain of the destination node. The process (i.e., steps1140, 1150, and 1160) is repeated until the desired coverage margin isachieved, at which point an antenna having the desired characteristicshas been identified and the design procedure is complete (see block1170). It should be understood that, in some circumstances, it may notbe possible to further alter any of the above-noted parameters, in whichcase a new antenna having improved gain characteristics may need to beselected (see block 1130), and the process repeated.

[0066] Embodiments of a computing device 100 having a multi-mode antennasystem 200 having been herein described, those of ordinary skill in theart will appreciate the advantages of such an antenna system. Theantenna system 200 provides for communications over any one or more ofmultiple modes. The multi-mode antenna system may be integrated into thehousing of a computer device, thereby minimizing system volume andconserving space for other components. In addition, the multi-modeantenna may be implemented on any computer platform, including a laptopcomputer, a notebook computer, a tablet style computer, a hand-heldcomputer (e.g., a PDA), or other portable computing device, as well asless mobile platforms such as desktop computers.

[0067] The foregoing detailed description and accompanying drawings areonly illustrative and not restrictive. They have been provided primarilyfor a clear and comprehensive understanding of the disclosed embodimentsand no unnecessary limitations are to be understood therefrom. Numerousadditions, deletions, and modifications to the embodiments describedherein, as well as alternative arrangements, may be devised by thoseskilled in the art without departing from the spirit of the disclosedembodiments and the scope of the appended claims.

What is claimed is:
 1. An antenna system comprising: a first antennaoperable in a first mode of communication between a computing device anda first node; a second antenna operable in a second mode ofcommunication between the computing device and a second node; and athird antenna operable in a third mode of communication between thecomputing device and a third node.
 2. The antenna system of claim 1,wherein the first mode of communication has an operating frequency in a2.4 to 2.4835 GHz band.
 3. The antenna system of claim 2, wherein thesecond mode of communication has an operating frequency in a 2.4 to2.4835 GHz band or a 5.15 to 5.825 GHz band.
 4. The antenna system ofclaim 3, wherein the third mode of communication has an operatingfrequency in a 450 to 1990 MHz band.
 5. The antenna system of claim 1,further comprising: a fourth antenna operable in a fourth mode ofcommunication between the computing device and a fourth node.
 6. Theantenna system of claim 5, wherein the first and second modes ofcommunications have an operating frequency in a 2.4 to 2.4835 GHz band,the third mode of communication has an operating frequency in the 450 to1990 MHz band, and the fourth mode of communication has an operatingfrequency in the 5.15 to 5.825 GHz band.
 7. The antenna system of claim1, wherein the first antenna has a range up to approximately 10 meters,the second antenna has a range up to approximately 100 meters, and thethird antenna has a range of approximately 100 meters and greater. 8.The antenna system of claim 1, wherein the first mode comprises awireless personal area network (PAN) connection, the second modecomprises a wireless local area network (LAN) connection, and the thirdmode comprises a wireless wide area network (WAN) connection.
 9. Acomputing device comprising: a housing; and an antenna system disposedon the housing, the antenna system operable in a first mode, operable ina second mode, and operable in a third mode.
 10. The computing device ofclaim 9, wherein the first mode has an operating frequency in a 2.4 to2.4835 GHz band.
 11. The computing device of claim 10, wherein thesecond mode has an operating frequency in a 2.4 to 2.4835 GHz band or a5.15 to 5.825 GHz band.
 12. The computing device of claim 11, whereinthe third mode has an operating frequency in a 450 to 1990 MHz band. 13.The computing device of claim 9, wherein the antenna system is operablein a fourth mode.
 14. The computing device of claim 13, wherein thefirst and second modes have an operating frequency in a 2.4 to 2.4835GHz band, the third mode has an operating frequency in the 450 to 1990MHz band, and the fourth mode has an operating frequency in the 5.15 to5.825 GHz band.
 15. The computing device of claim 9, wherein the firstmode is operable in a range up to approximately 10 meters, the secondmode is operable in a range up to approximately 100 meters, and thethird mode is operable in a range of approximately 100 meters andgreater.
 16. The computing device of claim 9, wherein the first modecomprises a wireless personal area network (PAN) connection, the secondmode comprises a wireless local area network (LAN) connection, and thethird mode comprises a wireless wide area network (WAN) connection. 17.The computing device of claim 9, further comprising: a display disposedin the housing; and a second housing movably coupled with the housing,the second housing including a keyboard.
 18. The computing device ofclaim 17, wherein the second housing is detachable from the housing. 19.The computing device of claim 17, further comprising a processing devicedisposed within the housing.
 20. The computing device of claim 17,further comprising a processing device disposed within the secondhousing.
 21. The computing device of claim 9, wherein the antenna systemincludes an artificial magnetic conductor (AMC) material.
 22. Thecomputing device of claim 21, wherein the AMC material shields at leasta portion of the antenna system from a processing device disposed withinthe housing.
 23. The computing device of claim 9, wherein the housingcomprises a metal material.
 24. The computing device of claim 23,wherein the antenna system includes an artificial magnetic conductor(AMC) material, the AMC material to isolate at least a portion of theantenna system from the housing.
 25. A computing device comprising: ahousing; a first antenna disposed on the housing, the first antennaoperable in a first mode; a second antenna disposed on the housing, thesecond antenna operable in a second mode; and a third antenna disposedon the housing, the third antenna operable in a third mode.
 26. Thecomputing device of claim 25, wherein the first mode has an operatingfrequency in a 2.4 to 2.4835 GHz band.
 27. The computing device of claim26, wherein the second mode has an operating frequency in a 2.4 to2.4835 GHz band or a 5.15 to 5.825 GHz band.
 28. The computing device ofclaim 27, wherein the third mode has an operating frequency in a 450 to1990 MHz band.
 29. The computing device of claim 25, further comprising:a fourth antenna disposed on the housing; wherein the fourth antenna isoperable in a fourth mode.
 30. The computing device of claim 29, whereinthe first and second modes have an operating frequency in a 2.4 to2.4835 GHz band, the third mode has an operating frequency in the 450 to1990 MHz band, and the fourth mode has an operating frequency in the5.15 to 5.825 GHz band.
 31. The computing device of claim 25, whereinthe first antenna has a range up to approximately 10 meters, the secondantenna has a range up to approximately 100 meters, and the thirdantenna has a range of approximately 100 meters and greater.
 32. Thecomputing device of claim 25, wherein the first mode comprises awireless personal area network (PAN) connection, the second modecomprises a wireless local area network (LAN) connection, and the thirdmode comprises a wireless wide area network (WAN) connection.
 33. Thecomputing device of claim 25, further comprising: a display disposed inthe housing; and a second housing movably coupled with the housing, thesecond housing including a keyboard.
 34. The computing device of claim33, wherein the second housing is detachable from the housing.
 35. Thecomputing device of claim 33, further comprising a processing devicedisposed within the housing.
 36. The computing device of claim 33,further comprising a processing device disposed within the secondhousing.
 37. The computing device of claim 25, wherein at least one ofthe first, second, and third antennas is disposed on a base comprisingan artificial magnetic conductor (AMC).
 38. The computing device ofclaim 37, wherein the AMC material shields the at least one antenna froma processing device disposed within the housing.
 39. The computingdevice of claim 37, wherein the at least one antenna has a thicknessthat does not exceed approximately 4 millimeters.
 40. The computingdevice of claim 25, further comprising: a cavity formed on an exteriorof the housing; wherein one of the first, second, and third antennas isdisposed in the cavity.
 41. The computing device of claim 40, whereinthe one antenna disposed in the cavity has a height less than a depth ofthe cavity.
 42. The computing device of claim 25, wherein at least oneof the first, second, and third antennas extends a height above anexterior surface of the housing that does not exceed approximately 4millimeters.
 43. The computing device of claim 25, wherein the housingcomprises a metal material.
 44. The computing device of claim 43,wherein one of the first, second, and third antennas includes anartificial magnetic conductor (AMC) material; the AMC material toisolate the one antenna from the housing.
 45. The computing device ofclaim 25, wherein at least two of the first, second, and third antennacomprise a single integrated antenna.
 46. A computing device comprising:a first generally rectangular-shaped housing; a second housing movablycoupled with a first edge of the first housing; a first antenna disposedon a second edge of the first housing, the first antenna operable in afirst mode; a second antenna disposed on a third edge of the firsthousing, the third edge opposing the first edge, the second antennaoperable in a second mode; and a third antenna disposed on a fourth edgeof the first housing, the fourth edge opposing the second edge, thethird antenna operable in a third mode.
 47. The computing device ofclaim 46, wherein the second housing is detachable from the firsthousing.
 48. The computing device of claim 46, wherein the first modehas an operating frequency in a 2.4 to 2.4835 GHz band.
 49. Thecomputing device of claim 48, wherein the second mode has an operatingfrequency in a 2.4 to 2.4835 GHz band or a 5.15 to 5.825 GHz band. 50.The computing device of claim 49, wherein the third mode has anoperating frequency in a 450 to 1990 MHz band.
 51. The computing deviceof claim 46, further comprising: a fourth antenna disposed on the thirdedge of the first housing, the fourth antenna operable in a fourth mode.52. The computing device of claim 51, wherein the first and second modeshave an operating frequency in a 2.4 to 2.4835 GHz band, the third modehas an operating frequency in the 450 to 1990 MHz band, and the fourthmode has an operating frequency in the 5.15 to 5.825 GHz band.
 53. Thecomputing device of claim 46, wherein the first antenna has a range upto approximately 10 meters, the second antenna has a range up toapproximately 100 meters, and the third antenna has a range ofapproximately 100 meters and greater.
 54. The computing device of claim46, wherein the first mode comprises a wireless personal area network(PAN) connection, the second mode comprises a wireless local areanetwork (LAN) connection, and the third mode comprises a wireless widearea network (WAN) connection.
 55. The computing device of claim 46,further comprising a display disposed in the first housing.
 56. Thecomputing device of claim 55, further comprising a processing devicedisposed within the first housing.
 57. The computing device of claim 55,further comprising a processing device disposed within the secondhousing.
 58. The computing device of claim 46, wherein at least one ofthe first, second, and third antennas is disposed on a base comprisingan artificial magnetic conductor (AMC).
 59. The computing device ofclaim 58, wherein the AMC material shields the at least one antenna froma processing device disposed within the first housing.
 60. The computingdevice of claim 46, wherein the first housing comprises a metalmaterial.
 61. The computing device of claim 60, wherein one of thefirst, second, and third antennas includes an artificial magneticconductor (AMC) material, the AMC material to isolate the one antennafrom the first housing.
 62. The computing device of claim 46, wherein atleast two of the first, second, and third antenna comprise a singleintegrated antenna.
 63. The computing device of claim 46, wherein atleast one of the first, second, and third antennas is attached to thefirst housing using an adhesive.
 64. The computing device of claim 46,wherein at least one of the first, second, and third antennas isattached to the first housing using a mechanical fastener.
 65. Thecomputing device of claim 46, wherein at least one of the first, second,and third antennas is mounted in a cavity formed on one of the edges ofthe first housing.
 66. A method comprising: establishing a firstwireless connection over a first mode using a first antenna of acomputing device; establishing a second wireless connection over asecond mode using a second antenna of the computing device; andestablishing a third wireless connection over a third mode using a thirdantenna of the computing device.
 67. The method of claim 66, wherein thefirst mode is conducted at a frequency in a 2.4 to 2.4835 GHz band. 68.The method of claim 67, wherein the second mode is conducted at afrequency in a 2.4 to 2.4835 GHz band or a 5.15 to 5.825 GHz band. 69.The method of claim 68, wherein the third mode is conducted at afrequency in a 450 to 1990 MHz band.
 70. The method of claim 66, whereintwo of the first, second, and third wireless connections aresimultaneously active.
 71. The method of claim 66, wherein the first,second, and third wireless connections are simultaneously active. 72.The method of claim 66, further comprising establishing a fourthwireless connection over a fourth mode using a fourth antenna of thecomputing device.
 73. The computing device of claim 72, wherein thefirst and second modes are conducted at a frequency in a 2.4 to 2.4835GHz band, the third mode is conducted at a frequency in the 450 to 1990MHz band, and the fourth mode is conducted at a frequency in the 5.15 to5.825 GHz band.
 74. A method comprising: selecting an antenna to providea specified coverage margin for an antenna system; measuring a gaincharacteristic of the antenna; determining a coverage margin based uponthe measured gain characteristic; and if the coverage margin does notmeet the specified coverage margin, altering a parameter.
 75. The methodof claim 74, further comprising: measuring a second gain characteristicof the antenna; and determining a second coverage margin based upon thesecond measured gain characteristic.
 76. The method of claim 74, furthercomprising: if the coverage margin meets the specified coverage margin,using the selected antenna in the antenna system.
 77. The method ofclaim 74, wherein the parameter comprises a transmission power, areceive sensitivity of a source node, or a gain characteristic of thesource node.
 78. The method of claim 74, wherein the antenna is selectedbased upon an estimated gain.
 79. The method of claim 78, wherein theestimated gain is determined from a transmission power, a receivesensitivity of a source node, a gain characteristic of the source node,a wavelength, a path loss characteristic, and a distance.